1. Technical Field
The present invention relates to a cleaning method and a cleaning apparatus wherein an object to be processed, such as a semiconductor wafer or a glass substrate for an LCD, is immersed in a cleaning liquid and a rinse liquid and cleaned.
2. Description of Related Art
A cleaning method that is widely used during the process of manufacturing semiconductor devices generally involves immersing objects to be processed, such as semiconductor wafers or glass substrates for LCDs (hereinafter called "wafers"), sequentially into a series of cleaning tanks, each filled with a chemical (processing liquid) such as ammonia water (NH.sub.4 OH) or hydrofluoric acid (HF) or a rinse liquid such as distilled water or ozone water, to clean them.
A so-called one-path type of apparatus is known in the art as one form of this cleaning apparatus, wherein a rinse liquid (such as distilled water or ozone water) and a dilute liquid (for example, diluted hydrofluoric acid (DHF) including a rinse liquid and a chemical) such as hydrofluoric acid (HF) are supplied in turn in the same processing tank, and a wafer or the like is immersed within this rinse liquid and diluted liquid for a predetermined time to clean it. With this cleaning apparatus, a dilute liquid (such as DHF) comprising a predetermined quantity of a chemical mixed into a rinse liquid is poured into the processing tank and the wafer or the like is immersed in this dilute liquid (DHF), or the dilute liquid is supplied into the processing tank after the wafer or the like has been accommodated therein, whereby an etching type of "cleaning" can be performed to remove particles adhering to the surfaces of the wafer or to remove metals such as Ni and Fe or natural oxide films that have adhered physically or chemically thereto. The wafer is subsequently immersed in rinse liquid that is supplied to the processing tank, so that any chemical adhering to the wafer surfaces can be removed.
In this prior-art type of cleaning apparatus, the time during which the wafer or the like is immersed and processed in the cleaning liquid is constant, so that if the temperature of the cleaning liquid within the processing tank changes, the wafer processing capability thereof will also change. With cleaning (etching) by DHF, for example, a problem occurs in that the etching characteristics will change, so that the cleaning capability and the cleaning precision thereof will deteriorate.
The present invention was devised in the light of the above situation and has as an object thereof the provision of a cleaning method and apparatus wherein control of processing time is based on the temperature of the cleaning liquid, thereby enabling improvements in cleaning capability and cleaning precision.